The technical basis of a remote control single rotor model helicopter is consistent with that of a real helicopter, but their structures are distinctly different. Currently, the control modes of a helicopter include Bell mode, Hiller mode, and Bell-Hiller mixed mode.
The Bell mode is mostly used in the real helicopter, and a typical feature of the mode is that a blade angle of rotor blades is directly controlled, no stabilizing blade is used, and a front edge of the rotor blades has a weight load. Most of the modern helicopters do not even have the weight load, instead the rotor blades perform a waving movement. During flying, when the helicopter encounters the interference of the unstable air flow, a changed aerodynamic load is not transmitted to the helicopter's body, so the helicopter can fly stably. The Bell mode helicopter is characterized in that the action control is relatively direct, so it is sensitive to small movements, but sharp maneuver fly cannot be realized. Therefore, this mode cannot realize the specific requirements on the maneuverability of the common trick model helicopter, that is, high sensitivity, difficult actions, and great rudder operations.
The features of the Hiller mode are opposite to those of the Bell mode, a Hiller control mode R/C helicopter has a pair of Hiller bars. The Hiller bars mainly serve as a medium between servos and main rotor blades. During operation, the Hiller bars are pulled by the servos, and then the main rotor blades are pulled through an aerodynamic force of the Hiller bars. The Hiller mode helicopter is suitable for the sharp maneuver fly, and is mostly applied to the R/C helicopter. However, it is difficult for the pure Hiller mode to obtain the enough stability.
Currently, the Bell-Hiller mixed mode is widely used in model helicopters. The operating procedure of an operating system of the “Bell-Hiller” mode is described in the following. According to an instruction of an electronic receiver in a radio remote control device, a servo controls a non-rotating swash plate to be inclined to a specified direction through a connecting rod. A rotating swash plate is driven by a shifting fork to rotate synchronously with a spindle on an inclined surface of the non-rotating swash plate. During the procedure, a transmission torque of the servo is converted to a cyclic torque. In each rotation cycle, the rotating swash plate pulls a pitch control rocker arm of the Hiller bars through connecting rods, so as to cyclically control an attack angle of the “Hiller” bars to increase or decrease, such that the rotated Hiller bars cyclically rise or fall. Further, the synchronously rotating pitch control rocker arm of the rotor blades is pulled by the connecting rods to change the attack angle, and a lift force of the rotating rotor blades is cyclically increased or decreased, such that a rotor disc of the rotor blades is inclined to a direction specified in the instruction, and a longitudinal torque and a transversal torque resulting from the inclined rotor disc of the rotor blade enable the operated model helicopter to move along the specified direction.
The features of the operating system in the “Bell-Hiller” mode are described in the following. The operation torque of the servo is transmitted to the rotor blades through the aerodynamic force of the “Hiller” bars serving as the medium, but the procedure is not entirely a mechanical transmission, such that the mode meets the demands for the difficult trick actions of the single rotor model helicopter with the great rudder operations. The balancing hammer and the Hiller bars in the “Bell-Hiller” mode are an integral combination, and an axial line of the Hiller bars of most model helicopters in the mode is perpendicular to an axial line of the rotor blades. Due to a gyro effect generated when the Hiller bars rotates, an interference from outside encountered by the model helicopter may be overcome, thereby slightly balancing the model helicopter, and enabling the model to overcome the interference from the outside automatically. However, the Hiller bars rotating under a certain speed has a damping function on the automatic balancing function. Due to the limit of the structure, the balancing function of the Hiller bars is weakened. The above features result in poor balance behavior of the single rotor model helicopter in the mode, and the operation techniques are complicated. In order to entirely master the operation techniques, a coach is required for training, much practice for a long term is needed for mastering the techniques, and the high technical threshold causes great limit to the model.
People in the industry intend to modify the “Bell-Hiller” mode helicopter, so as to improve the balance behavior, and lower the complexity and the difficulty of the operation techniques. However, the automatic balancing function of the balancing hammer and the auxiliary operation function of the Hiller bars are two different technical issues, which, however, are integrated as a whole in the Bell-Hiller mode. Therefore, the structure designed according to the mode cannot have a sufficient design freedom between the maneuverability and the balance behavior.
Despite the above limits, in the field of model helicopters, the application of the “Bell-Hiller” mode on the four-channel radio remote control helicopters or a higher level model becomes a habitual mode. For another coaxial dual-rotor blade model helicopter that can be easily mastered, rotation directions of upper and lower rotor blades are opposite, such that when the model helicopter is operated to travel, the aerodynamic performance of the rotor blades is quite different from that of the single rotor model helicopter, and correspondingly, the operating system and the balancing system have the following distinctive features. A balancing hammer controls the upper rotor blade to achieve fine stability behavior of the helicopter, and the operating system controls the lower rotor blade to operate longitudinal and transversal torques of the helicopter.
Therefore, in the past, when learning to operate the single rotor model helicopter, aero model fans can only select the “Bell-Hiller” mode single rotor model helicopter, which is difficult to master. Actually, the features of the “Bell-Hiller” mode single rotor model helicopter which is suitable for the great rudder operations and has sensitive operation become an obstacle. The operation techniques of the mode are complicated, and the balance behavior of the model helicopter is poor, so many people even cannot master the hovering technique, the basic flying operation of the “Bell-Hiller” mode helicopter, not to mention the trick actions with high difficulty and requiring great rudder operations. Therefore, it is necessary to break away from the habitual mode, and develop a single rotor model helicopter which can fly easily and can be operated more easily.